Gulf of Maine Seasonal Sea Surface Temperature Update
Seasonal Patterns in Sea Surface Temperatures
About the Updates:
Over the past decade, scientists at the Gulf of Maine Research Institute have led a body of research that highlights the rapid pace of warming in the Gulf of Maine. To keep you informed, we share seasonal updates about conditions in the Gulf of Maine.
Note About the Data: The figures in this report are created using remotely-sensed satellite data as part of publicly funded research efforts. Satellite SST data was obtained from NOAA’s National Center for Environmental Information (NCEI), with all maps and figures displaying NOAA’s Optimum Interpolation Sea Surface Temperature Data.
The Gulf of Maine Region
For analyses like these, it is important to be clear about the spatial extent that “defines” the Gulf of Maine (Figure 1), as different borders could produce different results. The spatial domain we use as the “Gulf of Maine” is displayed below. This area is consistent with previous seasonal and annual reports that scientists at GMRI have produced.
Summer Highlights
For this seasonal report we present an analysis of SST for summer (June 1, 2023 - August 31, 2023). During this season, the average SST for the Gulf of Maine was 61.01°F, making it the 8th hottest summer on record for the period of 1982-2023 — the period over which the satellite data used are available. This seasonal average temperature is 1.91°F above the 1991–2020 climatological reference period (CRP) spring average of 59.1°F.
Weekly Temperatures
In ?@tbl-season-temps we highlight how the SST for each week this summer compares to the 1991-2020 CRP for the area shown in Figure 1. The observed SST, long-term average SST, and SST anomalies (i.e., departures from the long-term average SST) are shown. Departures from the long-term average were 1°F or more above normal during March & April, with temperatures in May falling closest to the long-term average.
?(caption)
| Table 1. Weekly Averaged Sea Surface Temperatures - Summer | |||
| (June 1, 2023 - August 31, 2023) | |||
| One-Week Period | Observed Temperature | Climatological Average | Temperature Anomaly |
|---|---|---|---|
Jun 01 - Jun 03 |
53.8°F (12.1°C) |
50°F (10°C) |
3.78°F (2.1°C) |
Jun 04 - Jun 10 |
52.1°F (11.2°C) |
51.3°F (10.7°C) |
0.808°F (0.449°C) |
Jun 11 - Jun 17 |
54°F (12.2°C) |
53.1°F (11.7°C) |
0.982°F (0.545°C) |
Jun 18 - Jun 24 |
55.5°F (13.1°C) |
54.9°F (12.7°C) |
0.631°F (0.35°C) |
Jun 25 - Jul 01 |
58.9°F (14.9°C) |
56.8°F (13.8°C) |
2.11°F (1.17°C) |
Jul 02 - Jul 08 |
60.4°F (15.8°C) |
58.5°F (14.7°C) |
1.9°F (1.06°C) |
Jul 09 - Jul 15 |
62.5°F (17°C) |
59.9°F (15.5°C) |
2.59°F (1.44°C) |
Jul 16 - Jul 22 |
65.1°F (18.4°C) |
61.1°F (16.2°C) |
3.91°F (2.17°C) |
Jul 23 - Jul 29 |
66.5°F (19.2°C) |
62.1°F (16.7°C) |
4.43°F (2.46°C) |
Jul 30 - Aug 05 |
64.7°F (18.2°C) |
62.8°F (17.1°C) |
1.93°F (1.07°C) |
Aug 06 - Aug 12 |
63.9°F (17.7°C) |
63.3°F (17.4°C) |
0.617°F (0.343°C) |
Aug 13 - Aug 19 |
64.7°F (18.2°C) |
63.4°F (17.4°C) |
1.35°F (0.749°C) |
Aug 20 - Aug 26 |
64.1°F (17.8°C) |
63.2°F (17.4°C) |
0.851°F (0.473°C) |
Aug 27 - Aug 31 |
64.9°F (18.3°C) |
62.9°F (17.2°C) |
1.97°F (1.1°C) |
| Data Source: NOAA OISSTv2 Daily Sea Surface Temperature Data. | |||
| Climatological Reference Period: 1991-2020. | |||
Monthly Statistics
?@tbl-monthly-temps shows monthly average SST for summer 2023, where we see each month was nearly 2°F or more above the 1991-2020 CRP. July showed the largest deviation from the long-term climatological average, with an average SST anomaly of 3.12 °F.
?(caption)
| Table 2. Monthly Averaged Sea Surface Temperatures - Summer | ||||
| (June 1, 2023 - August 31, 2023) | ||||
| Month | Rank (1982-2023) | Observed Temperature | Climatological Average | Temperature Anomaly |
|---|---|---|---|---|
Jun |
9 |
54.9°F (12.7°C) |
53.5°F (11.9°C) |
1.38°F (0.766°C) |
Jul |
4 |
63.6°F (17.5°C) |
60.5°F (15.8°C) |
3.12°F (1.73°C) |
Aug |
12 |
64.4°F (18°C) |
63.2°F (17.3°C) |
1.22°F (0.676°C) |
| Data Source: NOAA OISSTv2 Daily Sea Surface Temperature Data. | ||||
| Climatological Reference Period: 1991-2020. | ||||
Seasonal Trends and Anomalies in Context
The Gulf of Maine is an area of particular interest to the scientific community because of the remarkable rate of warming it has experienced in recent years coupled with its importance as a major driver for the regional economy.
When looking at average summer temperatures from the beginning of the satellite record in 1982 Figure 2, there is a clear long-term increase, with SST’s warming at a rate of 1.05°F per decade. This rate of seasonal spring warming is ~4x the rate that global ocean temperatures are warming (0.27°F per decade).
The unprecedented levels of warmth over the past decade or so are consistent with what researchers believe has been a distinct regime shift in terms of the major influences on SSTs in the Gulf of Maine. The drivers of this (e.g., a potential weakening of the Atlantic Meridional Overturning Circulation, widening of the Gulf Stream, changes in the characteristics of the Labrador Current) have been well-documented in the peer-reviewed literature, including through research by GMRI scientists.
How Does this Summer Compare?
2023 is the 8th warmest summer season observed in the Gulf of Maine during the 41 years we have satellite data to analyze. The top 5 warmest summer seasons have all occurred in the last decade.
Marine Heatwave Conditions
The most commonly used definition of a “marine heatwave” (MHW) is when daily average SSTs exceeded the 90th percentile of a climatological (i.e., 30-year) average for at least 5 consecutive days. Gaps of 2 days or less in this threshold do not constitute a break in the MHW event.
Using this broadly accepted definition, the Gulf of Maine has experienced MHW conditions for 17% of this summer. May was the only month this Spring where SST was below the threshold of a MHW (90th Percentile).
Presenting SST conditions in terms of anomalies (Figure 5) as opposed to absolute values (Figure 4) illustrates in greater detail the magnitude of MHW conditions throughout the summer. The most extreme daily SST anomalies occurred in March, with temperatures exceeding 5°F above the climatological average.
Heatmap of Temperature Anomalies and Heatwave Events
Looking at the full record of daily SST anomalies in the Gulf of Maine (Figure 6), the distinct thermal regime shift beginning around 2010 is evident. Indeed, since 2012, the Gulf of Maine has experienced far more persistent MHW conditions (indicated by solid black lines) than at any other point in the satellite record.
Spatial Distribution of Seasonal Anomalies
From a spatial perspective, the Gulf of Maine and (most) surrounding areas experienced above average SSTs during summer 2023, but the warmest patches were to the south and east of Georges Bank, mostly outside the domain analyzed in preceding sections. The highest seasonally averaged anomaly of any location above was 5.07°F - along the southern edge of the domain analyzed.
Monthly Temperature Anomalies
Average monthly SST anomalies are shown in Figure 8. The warmest anomalies were observed in March and April and were largely confined to areas just beyond the region of study (i.e, beyond the continental shelf where the Gulf Stream and Labrador Current have significantly more influence on oceanic conditions).
North Atlantic Heat
2023 was a year with headline temperatures for the North Atlantic. A dramatic figure that was shared widely on social media was a version of figure 11. which captures just how profoundly hot this year’s temperatures were across the N. Atlantic. SST in the North Atlantic have been off the charts hot for much of the year drawing attention and concerns for the rapidly changing ocean environment.
In a departure from the now-familiar pattern of regionally concentrated warming, much of the attention this year was on large areas in the eastern Atlantic experiencing a large-scale MHW event. This summer scientists sounded the alarm over record setting temperatures for much of the Eastern Atlantic impacting population centers along the European coast and contributing to sweltering temperatures on land.
Data Sources:
NOAA_ERSST_V5 data provided by the NOAA/OAR/ESRL PSL, Boulder, Colorado, USA, from their Web site at https://psl.noaa.gov/data/gridded/data.noaa.ersst.v5.html.
NOAA High Resolution SST data provided by the NOAA/OAR/ESRL PSL, Boulder, Colorado, USA, from their Web site at https://psl.noaa.gov/data/gridded/data.noaa.oisst.v2.highres.html.
Citing This Work
If you would like to cite this report, please use:
Gulf of Maine Research Institute. 2022. Gulf of Maine Warming Update: Summer 2023